The invention is an lenticular stereogram and a method for making the same which provides full panoramagram capability from a stereo pair.
There is a substantial prior art in the patent and other literature discussing parallax panoramagram or lenticular stereogram technology. It is not our intention to provide a thorough review of the prior art, but rather to provide a background sufficient to orient one skilled in the art enough to fully appreciate the present disclosure.
Image selection, as Ives has stated, must take place at either the surface of the display or the eyes of the viewer. If the former, then an infinite number of views is required if the image is to be viewed from any location in front of the display. If the latter, then only two views are required. In practice, the interdigitated panoramagram, which is the most practical version of the art under discussion, uses only a handful of images, which may or may not provide acceptable image quality. See L. Lipton, xe2x80x9cThe Future of Autostereoscopic Electronic Displaysxe2x80x9d, SPIE Conference Proceedings #1669.
Initial panoramagram cameras provided optical or mechanical means, with either a moving slit or lenticular array, to create a continuum of views within each image column, but the precursor of the panoramagram, the interdigitated parallax stereogram, used sliced and alternated left and right images of a stereopair. This array may be viewed either through a raster barrier (which resembles a Ronchi grating) or an overlaid lenticular surface. In the case of the lenticular method, each lenticule covers an interdigitated set of images, or one column. For either the barrier or lenticular method, image selection is provided more or less at the plane of the display, and there is no requirement for individual viewing devices or eyewear. The lenticular screen typically has a surface of corduroy-like semi-cylindrical elements or lenticules, and has for the most part supplanted the raster barrier because it has much greater light transmission, and because stereo viewing zones are much larger than unwanted pseudo viewing zones.
The term xe2x80x9ccontinuumxe2x80x9d as used herein is an approximation in fact due to resolution limitations in any imaging medium or lens system, but the term is more descriptive of the methodology of imaging since no after-the-fact combination is required of separately photographed views. The major benefit of this approach, however derived, is that the observer has relatively good freedom of head placement and can see a stereoscopic image over a broad angle of view.
The interdigitated stereogram, on the other hand, requires exact placement of the eyes in a particular location, and if the head of the observer moves ever so slightly, a pseuodoscopic rather than a stereoscopic image will be seen. The parallax panoramagram is an improvement over the interdigitated parallax stereogram in that it allows for more freedom of view location with respect to the display since quite of bit of head movement is possible. The parallax panoramagram, by incorporating a continuum or multiplicity of views, allows for a wider horizontal angle of view of the display. As previously stated, these cameras are able to produce such a continuum by various means. (The vertical angle of view is not at issue since the lenticular screen is refractive only in the horizontal plane, and head movement up and down does not alter the stereoscopic effect.)
The panoramagram requires a time exposure in some embodiments. The temporally derived spatial parallax information which is captured during the exposure is transformed into the required spatial parallax information. As long as a time exposure is required, certain applications and the ability to shoot many types of subjects are limited. Moreover, panoramagram cameras are complex and costly instruments. Thus, inventors sought means to simplify the panoramagram process and preserve its best quality, namely that the image is more easily viewed than the more primitive interdigitated stereogram.
In a clever variation of the two view interdigitated stereogram, inventors created means to interdigitate a multiplicity of views, in some embodiments captured simultaneously with a number of cameras suitably spaced along a horizontal base. Resembling the interdigitated stereogram, the interdigitated panoramagram neatly attempts to combine the best aspects of both techniques. An array of cameras facing the subject is used to simultaneously photograph the subject, and the images are combined optically or with the aid of a computer to produce the necessary columns of information. In some cases, a single camera is preferred for shooting still-life images, and it is slid along a bar for successive exposures.
It should be noted for clarity that the literature of silver-based photographic panoramagraphy uses the term xe2x80x9cinterdigitatexe2x80x9d to describe the laying down of multiple perspective stripes of images within a column. However, computer graphics people often describe this process as xe2x80x9cinterleaving,xe2x80x9d which is an unfortunate term because it is easily confused with the term xe2x80x9cinterlacing,xe2x80x9d which is widely used to describe electronic displays but with an entirely different meaning.
The panoramagram and its variants have over the years been used for many applications, such as portraiture, advertising, product packaging and magazine reproduction. The technology has also been used for mass consumer snapshot applications with cameras using only three or four lenses.
In the past decade or so, products for snapshots have appeared using the interdigitated concept, but using only three or four lenses or views. While better than a interdigitated stereopair stereogram, the result falls far short of a true panoramagram or a decent interdigitated panoramagram with regard to depth effect and viewing angle. Such products have not had a great deal of commercial success in the marketplace.
In addition to the needs of those requiring still images, viewed either as reflective prints or transparencies, there is also the need for autostereoscopic panoramagram technology as applied to motion picture and electronic imaging displays. The art was applied to movies in the former Soviet Union. Here, a raster barrier was used to view interdigitated stereograms, each view projected with its own lens. After about two decades, the process was abandoned because audiences preferred the polarizing method of image selection since sitting with the head held rigidly was uncomfortable for most people.
There have been some recent attempts to apply the art to electronic displays. The flat matrix type display panel would, at first, appear to be a good fit because of its ability to provide exact registration of an image element with respect to the lenticular screen optical elements. As it turns out, the commercially available products have been disappointing because of poor image quality and the constraint on viewer head placement, as mentioned above. One way to solve the later problem is to employ head tracking technology to shift columns to maintain a stereo rather than a pseudo effect. However, this technology is costly and can only work for a single observer at a time.
One of the most important potential applications of the art is for autostereoscopic television, or 3D TV, which may be viewed without eyewear. Laboratory demonstrations have shown that multiple video projectors projecting to the rear of a screen can be viewed from the front through a lenticular array. But even the use of eight or so projectors still results in severe limitations of observer head movement, and obviously requires a large bandwidth if each image requires its own channel.
One key to making such a television display practical might be to use an approach in which only a stereo pair of images is transmitted, and by some means at the TV set itself, create the additional views required for a true panoramagram display and its attendant benefits. A number of research papers, mostly by workers in Japan and Western Europe, have been presented on this topic. A review of the papers shows that limited success has been achieved, and it is far from certain that a promising approach will be forthcoming because the techniques employed require enormous computational effort. Although a receiver capable of synthesizing a panoramagram out of a stereo pair will require both image storage and powerful computation ability to accomplish on-the-fly synthesis, more progress will have to be shown on the algorithmic level.
As we have seen, there are significant limitations in the prior art. Progress from the interdigitated stereogram to the panoramagram, and then to the interdigitated panoramagram, is significant. However, production of still images with a multiple camera/lens array is not practical for many applications such as consumer snapshot applications or motion picture cinematography. In addition, there are many workers using field sequential stereo displays on computer workstations (for example, for scientific visualization) and viewing the display with shuttering eyewear, and these workers have a need for hard copy.
There is no question that a continuous approach, as illustrated in terms of individual columnar structure, is far superior to any other method in terms of ease of viewing and depth effect. Thus, it would thus be highly desirable to produce a full panoramagram effect from a stereopair, since the aforementioned applications would become practical. There would be no need for a multiple lens/camera array and the ensuing complications for still photography. It is furthermore clear that the usual panoramagram is not a practical solution for motion pictures, which would preferably be carried out with at most two cameras for the production of a stereo pair. Moreover, projection would then be most conveniently carried out with but a single projector.
The present invention includes a panoramagram and a method for making the same from a pair of planostereoscopic source images. The pair of source images are, for example, a left image and a right image having different perspective views which are spaced apart in a horizontal plane. The left image may be considered the starting image and the right image the ending image, or vice versa. Control points are defined at corresponding locations in the source images, and each control point includes position and color information. A plurality of intermediate images are created by xe2x80x9cmorphingxe2x80x9d from the starting image to the ending image using position and color information from each of the corresponding locations. Preferably, the morphing process involves creating transformations of the source images based on the physical proximity from each control point; in other words, the transformation is affected strongly by control points which are nearby and is less affected by control points which are far away. The intermediate images and the source images are then interdigitated to create a single output image with a continuum of views ranging from the left image to the right image.
A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description of the invention and accompanying drawings which set forth an illustrative embodiment in which the principles of the invention are utilized.